The present invention relates to a sealing assembly which is advantageously applicable in meters, e.g. water, gas, electricity or heat meters. It also relates to a sealing device including such an assembly and to a meter including such a device.
In general, it is desired to ensure that an apparatus is kept safe when the apparatus is in the possession of a user who might seek to dismantle it for dishonest purposes. This applies in particular to meters for water, gas, electricity, or heat, where such meters are generally protected by seals.
Seals are known that are constituted by metal wires passing through a sealing device co-operating with the apparatus in question and having a metal endpiece at their ends, which endpiece is usually made of lead.
As a general rule, with electricity meters, sealing devices are used to seal the covers or terminal caps of the meter to their supports. Traditionally, the head of a screw is pierced by a diametral bore, and after the screw has been tightened, this bore is put into register with two radial setbacks that are in alignment and formed by a groove in the recess provided in the terminal cover to receive the head of the screw. A steel wire is then passed through the first setback, into the bore of the head, and then into the second setback. Thereafter both ends of the wire are embedded in a piece of lead. Thus, any attempt at loosening the screw automatically leads to the steel wire becoming unsealed or sheared since the two strands of the wire on either side of the head of the screw are both prevented from turning by the corresponding setbacks and they are both embedded in the lead.
An initial seal is put into place in the factory or on the user""s premises by the installer of the meter, once it has been checked that the meter is properly calibrated.
Thereafter, only authorized personnel are entitled to remove the seal. This applies to personnel involved with meter maintenance and repair, and once they have done their work, they put a new seal on the meter using sealing pliers that generally include the stamp of some official body.
Unfortunately, such sealing pliers carried by maintenance personnel can be purloined by users seeking to open a meter for fraudulent purposes and then have the possibility of closing it again complete with its seal before the visit of a meter reader.
The present invention makes it possible to reduce quite considerably the possibility of this type of situation by not giving installation and maintenance personnel sealing devices suitable for making a seal on the user""s premises, but instead giving them devices that are factory-sealed and ready for mounting in a manner that is not reversible without breaking the seal.
For this purpose, the sealing assembly of the invention is designed to co-operation with a screw provided with tightening means by being mounted therein in such a manner that once said assembly is sealed said tightening means are hidden in a manner that is not reversible except by destroying the seal, and further comprising breakable drive means suitable when the sealing assembly is subjected to a tightening action, for driving the screw in a tightening direction inside a receptacle provided for this purpose and for breaking once the screw becomes blocked, so as to prevent any loosening action being applied via the breakable drive means.
This assembly presents the advantage of enabling the material used for sealing purposes, usually lead, to be replaced with brass, aluminum, or plastic.
For environmental reasons it is preferable to avoid using lead. In addition, since lead is a soft material, it remains possible to open a seal without damaging the seal in visible manner, thereby opening the way to fraud.
Performing the sealing operation in a factory makes it possible firstly to use machines that are more sophisticated than a pair of pliers, so each seal can be marked with information such as: serial number; identity of distributor or installer; . . . . This makes it possible to keep a record of and to trace all seals made in this way.
In addition, sealing operations performed in the factory can be automated.
In an advantageous variant, the sealing assembly comprises a first piece in the form of a bushing suitable for being mounted to rotate freely on the shank of a screw.
Advantageously, the sealing assembly comprises closure piece designed to co-operate with the first piece to hide the tightening means of the screw.
In a particular embodiment, said breakable drive means are integrally formed with the closure piece.
In a variant embodiment, said breakable drive means comprise a peripheral element connected to the closure piece via at least one breakable strand.
In another variant embodiment, the breakable drive means comprise a peripheral element connected to the bushing via at least one breakable strand.
Advantageously, the breakable drive means comprise a key suitable for co-operating with the tightening means of the screw.
In a particular embodiment, said key is breakable.
In a variant embodiment, a sealing plate is provided to co-operate with the first piece in such a manner as to prevent access to the closure piece.
In a particular embodiment, the first piece has through means for passing a sealing wire, and the closure piece has through means suitable for co-operating with the through means of the first piece for passing a sealing wire.
Advantageously, the clamping means are designed to co-operate with a tightening tool.
The present invention also provides a sealing device comprising such a sealing assembly mounted on a screw.
Compared with traditional devices, this sealing device presents the advantage of being capable of using ordinary screws that are not pierced by a bore.
The present invention also provides a meter including such a sealing device. The meter can be installed on the user""s premises and can be sealed without sealing being performed on site; nevertheless, if so desired, sealing can still be done at the user""s premises.